They were women of the streets, prostitutes and drug addicts who one by one went missing from Vancouver's downtown east side, 50 of them since 1983. For years, police paid little heed, dismissing concerns that the women had been murdered, or that a serial killer was at work.

Now, 40 officers from a special task force that was set up last spring are sifting through the dirt of a pig farm outside of the largest city in Western Canada.

Littered with mounds of earth and rusting vehicles, the farm is home to two wealthy and eccentric brothers who wear biker clothing and throw large, boozy parties at the Piggy's Palace Good Times Society, the name they have given to their ramshackle abode.

One of the brothers, Robert Pickton, 52, was charged in 1997 with attempted murder and aggravated assault of a prostitute, although for reasons that are unclear, he was never prosecuted.

The Vancouver Sun has reported that police have found identification from two of the missing women on the site in Port Coquitlam. If it does turn out to be a mass burial ground, police in the province of British Columbia will have much to answer for in what may become one of the most sensational crime stories in Canadian history.

Relatives and friends of some of the missing women say they suggested police investigate suspicious activities at the pig farm at least three years ago. One prostitute told police that she had seen a bag of bloody clothing at the farm. Police dismissed the tips, saying they were unfounded.

"It makes me so angry, when I think maybe this could have been stopped back then," Joyce Lachance, whose niece Marnie Frey has not been seen since 1997, told The Globe and Mail newspaper.

For years, Vancouver area police did little to investigate the fate of the women who disappeared from the most desperate street scene in the country. Hundreds of addicts shoot up in public on Vancouver's downtown east side, and many turn tricks to support their habit.

Vancouver police are still saying very little, and have not confirmed that they have found any evidence of the missing women on the pig farm. They charged Robert Pickton with several weapons-related offences, but refuse to say whether he is a suspect in the investigation. The brothers' lawyer denies they are involved in any way.

Relatives of the missing women say they are encouraged by what police told them was a major development in the case. They have lived for years not knowing whether their daughters, sisters and nieces were dead or alive, but they are also sickened to think what police might find at the pig farm.

The investigation will be long and painstaking, and there is a chance that pigs on the farm may have destroyed crucial evidence. Experts say pigs will devour a human body, breaking bones to get at the marrow.

The potential breakthrough on the case comes less than a year after the Royal Canadian Mounted Police were called in to lead the special task force.

It reflects badly on the Vancouver police, who have been criticised by the families of the missing women for not taking their cases seriously enough. Had the women had not been prostitutes and drug addicts, relatives say, there is no question police would have been far more aggressive in investigating their disappearances.

The Vancouver police had rejected the possibility of a serial killer because they had no bodies. The force now concedes it could have done better.